The proliferation of social networking and other similar sites on the Internet has provided many new opportunities for users to interact with other users, as well as third parties such as advertisers, providers of applications or “apps,” and other businesses. The third parties enrich users' online experience by offering users access to products, services, and promotional offers. Often, however, it is difficult for users to interact with third parties while also protecting their own privacy. For example, some advertisers seek personal information about users for market research and targeting. The use policies of many sites require third parties to request permission from a user before receiving and using a user's personal information in this way. Whether by design or accident, however, user personal data sometimes reaches third parties without permission. Also, sometimes it is desirable or even necessary for the third party to have functional access to user personal information. For example, third parties must be able to identify users in order to provide products, services and promotional offers.